The last half of the 20th Century has seen the birth and evolution of both open cardiac surgery as well as minimally invasive surgery (MIS) applied to a wide variety of procedures. Until recently, however, the two surgical specialties evolved largely independently. The complexity of the cardiac procedures, the potential for sudden and catastrophic complications, and the lack of effective tools to provide optimal surgical access inhibited development of MIS techniques.
Although open heart surgery has been employed to treat heart disease, most often it has been applied to reestabllishing blood supply to the heart muscle itself. The principle objective is either to clear occluded arteries or to graft replacement vessels around the blockages. In the latter case, these coronary artery bypass graft (CABG) procedures are generally effective, but only for a limited time, usually a few to ten years. Traditional access to the heart requires a full sternotomy, forcible spreading of the sternal margins, and entry into the pericardium. Once inside the pericardium, manual manipulation of the heart is usually necessary to reach the blocked arteries. Currently, only makeshift manipulators and retractors are available for the surgeon to use in an attempt to position the heart to facilitate surgical access. Such crude tools include surgical gloves that have been inflated and tied off prior to placement under an organ and gauze pads that are also used to shim organs into position. However use of such primitive tools presents problems such as risk that the tools will inadvertently be left behind after the procedure is complete, risk of damage to the surface of the heart or pericardium during their placement and removal and lack of ability to perform real-time control of organ elevation and position. Other balloon devices have been disclosed that assist in removal of hollow organs and that move organs and other structures, such as the abdominal wall, away from the area of surgical interest. See Moll et al, International Application No. PCT/US92/04393; this and all other references cited herein are expressly incorporated by reference as if set forth herein in their entirety. The interior surface of the pericardium itself is a delicate, serous membrane within which the heart slides freely. Any trauma to this surface, or to the heart itself, can subsequently cause adhesions to form, and therefore any means of manipulation or retraction must be very gentle. Reoperation within the pericardium often reveals evidence of previous traumatic manipulation, such as extensive adhesions between the heart and pericardium which must be released before further manipulation can be attempted. There is presently an unfulfilled need for more sophisticated devices that will permit atraumatic manipulation and stabilization of the heart and other organs and allow the surgeon to manipulate organ positioning from outside the surgical cavity.
Situations requiring more extreme manipulation create even greater intraoperative risk such as the likelihood that heart function will be impaired, or may even cease. The extent of motion required for such functional impairment to occur varies by individual and may be due to any of several causes, including kinking of the great vessels. If the heart ceases to function, the surgeon is faced with two choices, either (1) perform cardiopulmonary bypass (CPB), stopping the heart, or (2) lessen the manipulation until function is restored. The advantage of CPB is that it maintains apparent heart function to the rest of the body and provides opportunity for temperature control of the blood and cardioplegia being infused. However, a disadvantage is the risk of blood and organ damage. Moreover, prolonged bypass of the heart can damage heart tissue. However, it is thought that maintaining the heart in a hypothermic state may limit the degree of heart muscle necrosis. While other devices have been disclosed that cool the heart (see Daily, U.S. Pat. No. 5,609,620), these devices are not capable of simultaneously lifting and positioning the heart. On the other hand, stopping the heart has the advantage of allowing the heart to be emptied of blood, thus reducing its volume. Such volume reduction may, accordingly, allow more freedom for heart manipulation within the pericardium. Given these choices, it would seem most advantageous to work within a range of manipulation in which heart function is not compromised. Although such an outcome is attractive in some ways, it complicates the surgical procedure by presenting the surgeon with a beating heart upon which to complete very intricate anastomoses. The most advantageous solution, which has been unavailable heretofore, would be to not compromise heart function, yet provide a fixed surgical surface that is not affected by heart motion. It is clear that with current techniques and tools available, no one solution is without problems, and risk of trauma to the chest, and its resulting complications, is considerable. It is not therefore surprising that the search for better methods continues.
Early techniques designed to avoid some of the drawbacks of open heart surgery led to catheter techniques that open stenotic regions and reestablish blood flow without requiring arterial grafting. This advance was successful from the standpoint that it virtually eliminated trauma and reestablished blood flow quickly. However, some stenoses are difficult to treat using this technique, and its effectiveness is of limited duration. Such limitations led to the use of stenting in an effort to prolong patency. However, even with these advances, problems exist, and therefore, the search for other solutions still continues.
The middle ground of CABG surgery, performed through minimal incisions, is now becoming attractive. CABG surgery allows alternative approaches to a full sternotomy, the traditional incision used in open heart surgery, such as (1) a partial lower sternotomy, from the xiphoid process up to the second intercostal space, terminating in a transverse division to free the sternal margins, or (2) a mini-left thoracotomy, with partial removal of the fourth, left rib. Other choices are also in use or are currently being considered. As in open surgery, manipulation of the heart is still required and in fact, as incision sizes decrease, the nature and extent of this manipulation may change, and, accordingly, the difficulty may increase. In planning such a minimal incision, the surgeon must consider not only the desired manipulation of the heart itself for access to the coronary arteries, but must also consider optimal access to vessels which will be used to bypass the occluded arteries. The only tools available for such delicate cardiac manipulation and positioning are rigid manipulators with sharp contact points that can cause tissue trauma or primitive positioning tools discussed previously such as inflated gloves and gauze pads, which, in this procedure, are even more difficult to place and remove given the smaller incision size. Similar concerns apply to cardiac valve procedures where the heart must be positioned so that the appropriate surgical tools can reach the inner structure of the heart, as opposed to its surface.
In summary, it is clear the surgeon must weigh many issues in choosing the best access for a cardiac procedure. Such issues include: (1) patient-specific anatomy, condition and disease (2) the requirements of the intended treatment, (3) the trauma likely to result, and (4) the likely risks of complications. Moreover, any procedure selected must align with the surgeon's own skill, knowledge, and comfort level. Any choice will involve some degree of compromise. However, the availability of better cardiac positioning and manipulation devices can expand the number of viable choices by reducing trauma to the patient and creating a surgical environment with better access and enhanced stabilization of the structures that are the subject of such delicate techniques.
Moreover, lack of such devices is an impediment to the advancement of surgical cardiac procedures. It is clear that incision size is trending downward, that future procedures may entail multiple incisions, and that, in time, "port" or cannula access may be the only technique used. As this reduced incision size evolves, the need for atraumatic manipulation and stabilization of the heart within the pericardium will increase markedly.
Although we have focused on the development of cardiac surgical techniques in the context of the evolution of the need for atraumatic positioning and manipulation devices, it is clear that need for such devices also exists in surgical procedures in other anatomic locations. For example, procedures that require lifting or positioning of solid organs including the liver and the spleen would be enhanced by the present invention.
Insofar as we are aware, there has been no disclosure of an inflatable manipulator that can atraumatically manipulate and stabilize organs for optional access during surgery, nor are such devices available. A need therefore exists for an inflatable organ manipulator which may include various enhancements for simultaneous organ cooling and monitoring and for dissecting adhesions. The following methods and apparatus more specifically can be used to place manipulators between the heart and the pericardium in order to manipulate and stabilize the heart's position and orientation, and to cool it during periods of prolonged bypass.